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Discussion Starter · #1 ·
Can anyone help with this question?


1. Is 600 lumens enough for a good picture? If so, on what type of screen?


2. Can I use SVGA to drive my projector with my computer and get good performance?


Thanks for ANY help.


Bill
 

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You want to try to achieve at least 20 ft-L for peak white.


The equation is :


Intensity (ft-L) = Lumens / Screen Size (sq-ft) * screen gain.


Please make sure you are using an accurate lumens rating. Most projector manufacturers inflate their lumens numbers by 25% or more and most screen manufacturers inflate their screen gain by a little as well.


Hope this helps.


-Mr. Wigggles
 

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"....Most projector manufacturers inflate their lumens numbers by 25% or more .."


I'd gio with the "or more" particularly 1 chip DLP projectors.


Also almost all of these digital projectors measure their light output at some really high color temperature, and by the time you calibrate it correctly, for real world colors, you have lost 25-45% of the rated Lumen output.


-- Cain
 

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Don Stewart from Stewart Screens recently reported the "real world" lumen output for the Sharp 9000 DLP. Are there other reliable, unbiased, reports available for the other projectors commonly discussed on this forum?
 

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Mr. Wiggles...a question...


Why 20 ftL? Most move theaters hit 12-14 ftL. Just wondering...


P.S. I am an acknowledged CRT bigot, but I'm not baiting you here...just want to understand where you are coming from. CRT-types would be hard pressed to hit anything close to 20! :)
 

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What you want is 16+ FL in a completely light controlled room after calibration and taking into account screen gain. Bulbs dim with age so if you start at 20 you will likely stay above 16 for the bulk of the bulb life.


As a former CRT bigot, (I have a D-ILA now), you can live with 10 or so. But you really miss out on how good the image can be by compromising like that.


You don't loose your color vision at 8.73 FL, it's a gradual process, so the same picture at 20FL will look better than at 10 FL even with the same contrast.


Also note that if you have ambient light, the above numbers go out the window. You may need 30-40 FL.


Hope this helps,

Phil


P.S. I went from a Runco 980 to a JVC G-11. Once I had it set up in my room, I painfully realized that the above was true and promptly went out and joined a G15 power buy. The G-11 is a great machine, just not for a 12' wide GreyHawk. :eek:
 

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>Intensity (ft-L) = Lumens / Screen Size (sq-ft) * screen gain.


This also assumes you use the entire panel of the projector.


Hope this makes some sense to you. It's pretty simple once you get the hang of it. What you really want to do is see some images from various projectors on various screens and see if you like them.


Here is an example for you to play with, (replace the number with something close to what you are using). I eventually decided to go with a Grayhawk screen with the expectation that newer projectors would be brighter.


4:3 projector with 1000 (real lumen) onto a 4:3 6'x8' screen

Screen

Gain

1.5 -> (1000/(6x8)) * 1.5 = 31.25 lumen/sq.ft.

1.0 -> (1000/(6x8)) * 1.0 = 20.8

0.8 -> (1000/(6x8)) * 0.8 = 16.7


4:3 projector with 500 (real lumen) onto a 4:3 6'X8' screen

Screen

Gain

1.5 -> (500/(6x8)) * 1.5 = 15.6 lumen/sq.ft.

1.0 -> (500/(6x8)) * 1.0 = 10.4

0.8 -> (500/(6x8)) * 0.8 = 8.4


So if you have a native 4:3 projector but you are projecting a 16:9 image you have less lumens since you have a letterboxed image. (This is the reason some of us want a Anamorphic lens to convert a tall skinny image on a 4:3 to a 16:9 image).


Mark Hunter has posted an excellent description of this sometime ago. (With nice images to show you what it really means).

-=-

Mark
 

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Guys you are going to scare our new guest.


I tried to keep it simply; but..


The reason movie theaters don't go higher than 15 ft-L is flicker becomes obvious.


When I say 20ft-L, that is only because that is the intensity that most TV's have eventhough they could be much brighter if they didn't use such a dark tube (which has its own advantages)


I try to get at least 30 ft-L in my set-up. It is a matter of personal preference to some degree. You definitely want to avoid going below 12 ft-L - your colors and your details will sufer no matter how dark the room is.


-Mr. Wigggles
 

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We should note for billr's benefit that the 16/20 ft-lambert figure is based on a true "home-theater" setup, vs. a "media-room" style setup, and that in the former, the room is 100% light controlled to duplicate the theater experience.


In a not well light controlled room, or if billr likes a little ambient light, he will need much more light output. I like a little bit of ambient light, and I run at about 40 ft-lamberts most of the time.
 

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If advice was good, people would sell it not give it way so here is my opinion not advice:

To me 600 lummnes is defenetely not enough, nothing less the 2500 lummens is good enough for a good picture I believe if you can afford get the brightest.

There is no such a thing too bright, But too many not bright enough. Rick
 

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Hey Wiggles, nice to see you back. I've been dormant a while myself.


I'm no mathematician, but the formula seems to increase the lumens as the screen gain DECREASES, because the denominator gets smaller when you multiply your screen sq. footage by the lower gain number. Somethings wrong there. What's up?
 

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Okay, can you give me an example? It's pretty late, and I've had a tough month or two.
 

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I’ve slugged the output of my (Smart 2ed) VW10HT down to 350 (rated) lumens with a neutral density filter and use it with a high gain (da-lite hi power) screen.


Why? Because my walls are light (neither my wife nor my landlord looked impressed when I suggested painting them black) and the projector sits just above my head (makes a great hairdryer). So I’m in the sweet spot of a hi gain screen and the gain helps minimise light washing off the screen onto the walls. The room is otherwise unlit apart from street lamps outside (and the screen serves as a windown blind so no light falls on it).


Using rated specs it still makes the 20F/L grade (8ft wide 16*9 screen). Certainly the snap and depth of the image are better than without the ND filter. The penalty, the picture definitely is too dark anywhere but on the favoured sofa, still we never have guests :)
 
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